Micro-electromechanical nozzle arrangement having cantilevered actuator

ABSTRACT

A micro-electromechanical nozzle arrangement for an inkjet printhead includes a substrate defining an inverted pyramidal ink chamber with a vertex thereof terminating at an ink supply channel defined by the substrate, said substrate having a layer of CMOS drive circuitry; a roof structure connected to the drive circuitry layer and covering the ink chamber, the roof structure defining a fluid ejection nozzle rim above said chamber; a plurality of actuators fast with and displaceable with respect to the roof structure, the actuators radially spaced about the nozzle rim between the guide rails, each actuator having a serpentine heater element configured to expand thermally upon receiving current from the drive circuitry thereby moving said actuators into the chamber and increasing a fluid pressure inside the chamber to eject a drop of ink via the ejection nozzle, wherein each actuator is cantilevered to a heater element in a bendable manner; and a central arm which having metal and PTFE portions to provide structural support for the actuators.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 12/205,911 filed Sep. 7, 2008, which is a continuation application of U.S. Ser. No. 11/965,722 filed on Dec. 27, 2007, now issued U.S. Pat. No. 7,438,391, which is a continuation application of U.S. Ser. No. 11/442,126 filed on May 30, 2006, now issued as U.S. Pat. No. 7,326,357, which is a continuation application of U.S. Ser. No. 10/728,924 filed on Dec. 8, 2003, now issued as U.S. Pat. No. 7,179,395, which is a continuation application of U.S. Ser. No. 10/303,291 filed on Nov. 23, 2002, now U.S. Pat. No. 6,672,708, which is a continuation application of U.S. Ser. No. 09/855,093 filed on May 14, 2001, now U.S. Pat. No. 6,505,912 which is a continuation application of U.S. Ser. No. 09/112,806 filed 10 Jul. 1998, now U.S. Pat. No. 6,247,790. The disclosure of U.S. Pat. No. 6,672,708, U.S. Pat. No. 6,505,912 and U.S. Pat. No. 6,247,790 is specifically incorporated herein by reference.

CROSS- REFERENCED AUSTRALIAN US PATENT/PATENT APPLICATION Provisional Patent (Claiming Right of Priority from Application No. Australian Provisional Application) Docket No. PO7991 6,750,901 ART01US PO8505 6,476,863 ART02US PO7988 6,788,336 ART03US PO9395 6,322,181 ART04US PO8017 6,597,817 ART06US PO8014 6,227,648 ART07US PO8025 6,727,948 ART08US PO8032 6,690,419 ART09US PO7999 6,727,951 ART10US PO8030 6,196,541 ART13US PO7997 6,195,150 ART15US PO7979 6,362,868 ART16US PO7978 6,831,681 ART18US PO7982 6,431,669 ART19US PO7989 6,362,869 ART20US PO8019 6,472,052 ART21US PO7980 6,356,715 ART22US PO8018 6,894,694 ART24US PO7938 6,636,216 ART25US PO8016 6,366,693 ART26US PO8024 6,329,990 ART27US PO7939 6,459,495 ART29US PO8501 6,137,500 ART30US PO8500 6,690,416 ART31US PO7987 7,050,143 ART32US PO8022 6,398,328 ART33US PO8497 7,110,024 ART34US PO8020 6,431,704 ART38US PO8504 6,879,341 ART42US PO8000 6,415,054 ART43US PO7934 6,665,454 ART45US PO7990 6,542,645 ART46US PO8499 6,486,886 ART47US PO8502 6,381,361 ART48US PO7981 6,317,192 ART50US PO7986 6,850,274 ART51US PO8026 6,646,757 ART53US PO8028 6,624,848 ART56US PO9394 6,357,135 ART57US PO9397 6,271,931 ART59US PO9398 6,353,772 ART60US PO9399 6,106,147 ART61US PO9400 6,665,008 ART62US PO9401 6,304,291 ART63US PO9403 6,305,770 ART65US PO9405 6,289,262 ART66US PP0959 6,315,200 ART68US PP1397 6,217,165 ART69US PP2370 6,786,420 DOT01US PO8003 6,350,023 Fluid01US PO8005 6,318,849 Fluid02US PO8066 6,227,652 IJ01US PO8072 6,213,588 IJ02US PO8040 6,213,589 IJ03US PO8071 6,231,163 IJ04US PO8047 6,247,795 IJ05US PO8035 6,394,581 IJ06US PO8044 6,244,691 IJ07US PO8063 6,257,704 IJ08US PO8057 6,416,168 IJ09US PO8056 6,220,694 IJ10US PO8069 6,257,705 IJ11US PO8049 6,247,794 IJ12US PO8036 6,234,610 IJ13US PO8048 6,247,793 IJ14US PO8070 6,264,306 IJ15US PO8067 6,241,342 IJ16US PO8001 6,247,792 IJ17US PO8038 6,264,307 IJ18US PO8033 6,254,220 IJ19US PO8002 6,234,611 IJ20US PO8068 6,302,528 IJ21US PO8062 6,283,582 IJ22US PO8034 6,239,821 IJ23US PO8039 6,338,547 IJ24US PO8041 6,247,796 IJ25US PO8004 6,557,977 IJ26US PO8037 6,390,603 IJ27US PO8043 6,362,843 IJ28US PO8042 6,293,653 IJ29US PO8064 6,312,107 IJ30US PO9389 6,227,653 IJ31US PO9391 6,234,609 IJ32US PP0888 6,238,040 IJ33US PP0891 6,188,415 IJ34US PP0890 6,227,654 IJ35US PP0873 6,209,989 IJ36US PP0993 6,247,791 IJ37US PP0890 6,336,710 IJ38US PP1398 6,217,153 IJ39US PP2592 6,416,167 IJ40US PP2593 6,243,113 IJ41US PP3991 6,283,581 IJ42US PP3987 6,247,790 IJ43US PP3985 6,260,953 IJ44US PP3983 6,267,469 IJ45US PO7935 6,224,780 IJM01US PO7936 6,235,212 IJM02US PO7937 6,280,643 IJM03US PO8061 6,284,147 IJM04US PO8054 6,214,244 IJM05US PO8065 6,071,750 IJM06US PO8055 6,267,905 IJM07US PO8053 6,251,298 IJM08US PO8078 6,258,285 IJM09US PO7933 6,225,138 IJM10US PO7950 6,241,904 IJM11US PO7949 6,299,786 IJM12US PO8060 6,866,789 IJM13US PO8059 6,231,773 IJM14US PO8073 6,190,931 IJM15US PO8076 6,248,249 IJM16US PO8075 6,290,862 IJM17US PO8079 6,241,906 IJM18US PO8050 6,565,762 IJM19US PO8052 6,241,905 IJM20US PO7948 6,451,216 IJM21US PO7951 6,231,772 IJM22US PO8074 6,274,056 IJM23US PO7941 6,290,861 IJM24US PO8077 6,248,248 IJM25US PO8058 6,306,671 IJM26US PO8051 6,331,258 IJM27US PO8045 6,110,754 IJM28US PO7952 6,294,101 IJM29US PO8046 6,416,679 IJM30US PO9390 6,264,849 IJM31US PO9392 6,254,793 IJM32US PP0889 6,235,211 IJM35US PP0887 6,491,833 IJM36US PP0882 6,264,850 IJM37US PP0874 6,258,284 IJM38US PP1396 6,312,615 IJM39US PP3989 6,228,668 IJM40US PP2591 6,180,427 IJM41US PP3990 6,171,875 IJM42US PP3986 6,267,904 IJM43US PP3984 6,245,247 IJM44US PP3982 6,315,914 IJM45US PP0895 6,231,148 IR01US PP0869 6,293,658 IR04US PP0887 6,614,560 IR05US PP0885 6,238,033 IR06US PP0884 6,312,070 IR10US PP0886 6,238,111 IR12US PP0877 6,378,970 IR16US PP0878 6,196,739 IR17US PP0883 6,270,182 IR19US PP0880 6,152,619 IR20US PO8006 6,087,638 MEMS02US PO8007 6,340,222 MEMS03US PO8010 6,041,600 MEMS05US PO8011 6,299,300 MEMS06US PO7947 6,067,797 MEMS07US PO7944 6,286,935 MEMS09US PO7946 6,044,646 MEMS10US PP0894 6,382,769 MEMS13US

TECHNICAL FIELD

The present invention relates to the field of inkjet printing and, in particular, discloses an inverted radial back-curling thermoelastic ink jet printing mechanism.

BACKGROUND

Many different types of printing mechanisms have been invented, a large number of which are presently in use. The known forms of printers have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles, has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different forms. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including a step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode form of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 which discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclose ink jet printing techniques which rely on the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction and operation, durability and consumables.

SUMMARY

According to an aspect of the present disclosure, a micro-electromechanical nozzle arrangement for an inkjet printhead includes a substrate defining an inverted pyramidal ink chamber with a vertex thereof terminating at an ink supply channel defined by the substrate, said substrate having a layer of CMOS drive circuitry; a roof structure connected to the drive circuitry layer and covering the ink chamber, the roof structure defining a fluid ejection nozzle rim above said chamber; a plurality of actuators fast with and displaceable with respect to the roof structure, the actuators radially spaced about the nozzle rim between the guide rails, each actuator having a serpentine heater element configured to expand thermally upon receiving current from the drive circuitry thereby moving said actuators into the chamber and increasing a fluid pressure inside the chamber to eject a drop of ink via the ejection nozzle, wherein each actuator is cantilevered to a heater element in a bendable manner; and a central arm which having metal and PTFE portions to provide structural support for the actuators.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIGS. 1-3 are schematic sectional views illustrating the operational principles of the preferred embodiment;

FIG. 4( a) and FIG. 4( b) are again schematic sections illustrating the operational principles of the thermal actuator device;

FIG. 5 is a side perspective view, partly in section, of a single nozzle arrangement constructed in accordance with the preferred embodiments;

FIGS. 6-13 are side perspective views, partly in section, illustrating the manufacturing steps of the preferred embodiments;

FIG. 14 illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of the preferred embodiment;

FIG. 15 provides a legend of the materials indicated in FIGS. 16 to 23; and

FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing steps in one form of construction of a nozzle arrangement in accordance with the invention.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, ink is ejected out of a nozzle chamber via an ink ejection port using a series of radially positioned thermal actuator devices that are arranged about the ink ejection port and are activated to pressurize the ink within the nozzle chamber thereby causing the ejection of ink through the ejection port.

Turning now to FIGS. 1, 2 and 3, there is illustrated the basic operational principles of the preferred embodiment. FIG. 1 illustrates a single nozzle arrangement 1 in its quiescent state. The arrangement 1 includes a nozzle chamber 2 which is normally filled with ink so as to form a meniscus 3 in an ink ejection port 4. The nozzle chamber 2 is formed within a wafer 5. The nozzle chamber 2 is supplied with ink via an ink supply channel 6 which is etched through the wafer 5 with a highly isotropic plasma etching system. A suitable etcher can be the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom.

A top of the nozzle arrangement 1 includes a series of radially positioned actuators 8, 9. These actuators comprise a polytetrafluoroethylene (PTFE) layer and an internal serpentine copper core 17. Upon heating of the copper core 17, the surrounding PTFE expands rapidly resulting in a generally downward movement of the actuators 8, 9. Hence, when it is desired to eject ink from the ink ejection port 4, a current is passed through the actuators 8, 9 which results in them bending generally downwards as illustrated in FIG. 2. The downward bending movement of the actuators 8, 9 results in a substantial increase in pressure within the nozzle chamber 2. The increase in pressure in the nozzle chamber 2 results in an expansion of the meniscus 3 as illustrated in FIG. 2.

The actuators 8, 9 are activated only briefly and subsequently deactivated. Consequently, the situation is as illustrated in FIG. 3 with the actuators 8, 9 returning to their original positions. This results in a general inflow of ink back into the nozzle chamber 2 and a necking and breaking of the meniscus 3 resulting in the ejection of a drop 12. The necking and breaking of the meniscus 3 is a consequence of the forward momentum of the ink associated with drop 12 and the backward pressure experienced as a result of the return of the actuators 8, 9 to their original positions. The return of the actuators 8,9 also results in a general inflow of ink from the channel 6 as a result of surface tension effects and, eventually, the state returns to the quiescent position as illustrated in FIG. 1.

FIGS. 4( a) and 4(b) illustrate the principle of operation of the thermal actuator. The thermal actuator is preferably constructed from a material 14 having a high coefficient of thermal expansion. Embedded within the material 14 are a series of heater elements 15 which can be a series of conductive elements designed to carry a current. The conductive elements 15 are heated by passing a current through the elements 15 with the heating resulting in a general increase in temperature in the area around the heating elements 15. The position of the elements 15 is such that uneven heating of the material 14 occurs. The uneven increase in temperature causes a corresponding uneven expansion of the material 14. Hence, as illustrated in FIG. 4( b), the PTFE is bent generally in the direction shown.

In FIG. 5, there is illustrated a side perspective view of one embodiment of a nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber 2 is formed with an isotropic surface etch of the wafer 5. The wafer 5 can include a CMOS layer including all the required power and drive circuits. Further, the actuators 8, 9 each have a leaf or petal formation which extends towards a nozzle rim 28 defining the ejection port 4. The normally inner end of each leaf or petal formation is displaceable with respect to the nozzle rim 28. Each activator 8, 9 has an internal copper core 17 defining the element 15. The core 17 winds in a serpentine manner to provide for substantially unhindered expansion of the actuators 8, 9. The operation of the actuators 8, 9 is as illustrated in FIG. 4( a) and FIG. 4( b) such that, upon activation, the actuators 8 bend as previously described resulting in a displacement of each petal formation away from the nozzle rim 28 and into the nozzle chamber 2. The ink supply channel 6 can be created via a deep silicon back edge of the wafer 5 utilizing a plasma etcher or the like. The copper or aluminium core 17 can provide a complete circuit. A central arm 18 which can include both metal and PTFE portions provides the main structural support for the actuators 8, 9.

Turning now to FIG. 6 to FIG. 13, one form of manufacture of the nozzle arrangement 1 in accordance with the principles of the preferred embodiment is shown. The nozzle arrangement 1 is preferably manufactured using microelectromechanical (MEMS) techniques and can include the following construction techniques:

As shown initially in FIG. 6, the initial processing starting material is a standard semi-conductor wafer 20 having a complete CMOS level 21 to a first level of metal. The first level of metal includes portions 22 which are utilized for providing power to the thermal actuators 8, 9.

The first step, as illustrated in FIG. 7, is to etch a nozzle region down to the silicon wafer 20 utilizing an appropriate mask.

Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene (PTFE) is deposited and etched so as to define vias 24 for interconnecting multiple levels.

Next, as illustrated in FIG. 9, the second level metal layer is deposited, masked and etched to define a heater structure 25. The heater structure 25 includes via 26 interconnected with a lower aluminium layer.

Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE is deposited and etched to the depth of 1 μm utilizing a nozzle rim mask to define the nozzle rim 28 in addition to ink flow guide rails 29 which generally restrain any wicking along the surface of the PTFE layer. The guide rails 29 surround small thin slots and, as such, surface tension effects are a lot higher around these slots which in turn results in minimal outflow of ink during operation.

Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzle and actuator mask to define a port portion 30 and slots 31 and 32.

Next, as illustrated in FIG. 12, the wafer is crystallographically etched on a <111> plane utilizing a standard crystallographic etchant such as KOH. The etching forms a chamber 33, directly below the port portion 30.

In FIG. 13, the ink supply channel 34 can be etched from the back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of United Kingdom. An array of ink jet nozzles can be formed simultaneously with a portion of an array 36 being illustrated in FIG. 14. A portion of the printhead is formed simultaneously and diced by the STS etching process. The array 36 shown provides for four column printing with each separate column attached to a different colour ink supply channel being supplied from the back of the wafer. Bond pads 37 provide for electrical control of the ejection mechanism.

In this manner, large pagewidth printheads can be fabricated so as to provide for a drop-on-demand ink ejection mechanism.

One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

-   -   1. Using a double-sided polished wafer 60, complete a 0.5         micron, one poly, 2 metal CMOS process 61. This step is shown in         FIG. 16. For clarity, these diagrams may not be to scale, and         may not represent a cross section though any single plane of the         nozzle. FIG. 15 is a key to representations of various materials         in these manufacturing diagrams, and those of other cross         referenced ink jet configurations.     -   2. Etch the CMOS oxide layers down to silicon or second level         metal using Mask 1. This mask defines the nozzle cavity and the         edge of the chips. This step is shown in FIG. 16.     -   3. Deposit a thin layer (not shown) of a hydrophilic polymer,         and treat the surface of this polymer for PTFE adherence.     -   4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 62.     -   5. Etch the PTFE and CMOS oxide layers to second level metal         using Mask 2. This mask defines the contact vias for the heater         electrodes. This step is shown in FIG. 17.     -   6. Deposit and pattern 0.5 microns of gold 63 using a lift-off         process using Mask 3. This mask defines the heater pattern. This         step is shown in FIG. 18.     -   7. Deposit 1.5 microns of PTFE 64.     -   8. Etch 1 micron of PTFE using Mask 4. This mask defines the         nozzle rim 65 and the rim at the edge 66 of the nozzle chamber.         This step is shown in FIG. 19.     -   9. Etch both layers of PTFE and the thin hydrophilic layer down         to silicon using Mask 5. This mask defines a gap 67 at inner         edges of the actuators, and the edge of the chips. It also forms         the mask for a subsequent crystallographic etch. This step is         shown in FIG. 20.     -   10. Crystallographically etch the exposed silicon using KOH.         This etch stops on <111> crystallographic planes 68, forming an         inverted square pyramid with sidewall angles of 54.74 degrees.         This step is shown in FIG. 21.     -   11. Back-etch through the silicon wafer (with, for example, an         ASE Advanced Silicon Etcher from Surface Technology Systems)         using Mask 6. This mask defines the ink inlets 69 which are         etched through the wafer. The wafer is also diced by this etch.         This step is shown in FIG. 22.     -   12. Mount the printheads in their packaging, which may be a         molded plastic former incorporating ink channels which supply         the appropriate color ink to the ink inlets 69 at the back of         the wafer.     -   13. Connect the printheads to their interconnect systems. For a         low profile connection with minimum disruption of airflow, TAB         may be used. Wire bonding may also be used if the printer is to         be operated with sufficient clearance to the paper.     -   14. Fill the completed print heads with ink 70 and test them. A         filled nozzle is shown in FIG. 23.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing systems including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. 

1. A micro-electromechanical nozzle arrangement for an inkjet printhead, said arrangement comprising: a substrate defining an inverted pyramidal ink chamber with a vertex thereof terminating at an ink supply channel defined by the substrate, said substrate having a layer of CMOS drive circuitry; a roof structure connected to the drive circuitry layer and covering the ink chamber, the roof structure defining a fluid ejection nozzle rim above said chamber; a plurality of actuators fast with and displaceable with respect to the roof structure, the actuators radially spaced about the nozzle rim between the guide rails, each actuator having a serpentine heater element configured to expand thermally upon receiving current from the drive circuitry thereby moving said actuators into the chamber and increasing a fluid pressure inside the chamber to eject a drop of ink via the ejection nozzle, wherein each actuator is cantilevered to a heater element in a bendable manner; and a central arm which having metal and PTFE portions to provide structural support for the actuators.
 2. The nozzle arrangement of claim 1, further comprising a series of struts interspersed between the actuators to support the nozzle rim.
 3. The nozzle arrangement of claim 1, wherein the serpentine heater element is made from gold.
 4. The nozzle arrangement of claim 1, wherein the roof structure includes ink flow guide rails to minimize wicking along the nozzle rim according to surface tension effects of ink in the chamber.
 5. The nozzle arrangement of claim 1, wherein the actuators include a polytetrafluoroethylene (PTFE) layer.
 6. The nozzle arrangement of claim 1, wherein the ink supply channel is created by means of a deep silicon back etch of the substrate utilizing a plasma etcher. 